1. Field of the Invention
The present invention is related to a system to treat diseases by substituting native biological regulatory function. More particularly, the present invention provides a system to treat diseases by substituting native biological regulatory function that is capable of regulating organs as if their central controllers were normally functioning even if the central controllers themselves become abnormal due to various causes. The invention includes a cardiac pacing system, a blood pressure regulating system, and a cardiac disease treatment system, all of which are particular embodiments of the medical treatment system.
2. Description of the Related Art
Heart transplantation from brain dead subjects became legal in Japan to treat patients with severe heart failure. However, the number of heart donors is definitely small, and the shortage of hearts for transplantation has been seriously discussed worldwide.
An alternative treatment for patients with severe heart failure is artificial heart implantation. However, even the most recent artificial hearts are not regulated by native biological regulation, thereby they do not always operate in concert with native organs.
Pacemakers have been used for the treatment of patients with bradycardia. Pacemakers enable necessary rhythmic myocardial contraction by electrically stimulating the myocardium artificially.
Recently rate-responsive pacemakers have been developed, in which stimulation rate changes according to the estimated native heart rate from e.g., electrocardiographic QT time, body temperature, or body acceleration. However, specificity, sensitivity and transient response of heart rate regulation compared to native heart rate regulation by such pacemakers have not always been satisfactory.
In some other diseases, it is well known that abnormal native regulatory function promotes disease processes. For example, it is known that abnormal native regulatory mechanisms participate in the progression of heart disease, and it is well known that sympathetic nerve overactivation and abnormal vagal nerve withdrawal occur after the onset of acute myocardial infarction, and worsens the outcome.
Such abnormal native regulatory function can also be observed in circulatory diseases other than heart diseases.
Even in normal subjects, 300 to 800 mL of blood shifts to the lower extremities and internal organs below the heart level during standing, causing decreased venous return to the heart and hypotension. Normal subjects usually have a blood pressure regulating mechanism to counteract this and to maintain a constant blood pressure, thereby preventing orthostatic hypotension. Subjects with various disorders and a damaged blood pressure regulating system, however, suffer from orthostatic hypotension. For example, in patients with Shy-Drager syndrome, a part of the nervous system involved in blood pressure regulation becomes abnormal, and quality of life is seriously impaired due to large fluctuations in blood pressure with their body position change.
Artificial organs and artificial devices, such as conventional artificial hearts and cardiac pacemakers, do not always operate in concert with native organs, as described above, because they are not intended to be controlled by the native regulatory system. Therefore their performance, in terms of sensitivity to changes in the native organs, is not satisfactory.
Pharmacological treatment with drugs such as coronary vasodilators, β-adrenergic blockers and anti-platelet agents, catheter-based interventional treatment, and coronary artery bypass surgery have been developed as treatments for myocardial infarction.
However, even when taking full advantage of all of the pharmacological, interventional and surgical treatments available, progression of pathology even to death is often inevitable.
Adrenergic agonists, such as epinephrine, levodopa and amphetamine, are used for pharmacological treatment of Shy-Drager syndrome with severe orthostatic hypertension, and excessive salt is administered for symptomatic relief. Although symptoms can be alleviated to some extent, it is impossible to treat Shy-Drager syndrome and restore full function.
The present invention provides a system to treat diseases that is capable of regulating organs as if their central controllers were normally functioning even if the central controllers themselves become abnormal by various causes. The present invention includes embodiments directed to a cardiac pacing system, a blood pressure regulating system, and a cardiac disease treatment system, all of which are based on the above medical treatment system.